1. Field of the Invention
The present invention relates to a liquid crystalline composition comprising a liquid-crystal compound, an optically anisotropic film formed of the liquid crystalline composition, an optical film comprising an optically anisotropic layer formed of the liquid crystalline composition, and a polarizer and a liquid-crystal display device comprising the optical film.
2. Related Art
Recently proposed is use of an optical compensatory sheet comprising a transparent support and an optically anisotropic layer of a discotic liquid crystalline composition thereon, in place of a stretched birefringent film. In general, the optically anisotropic layer is formed by applying a liquid crystalline composition containing a liquid-crystal compound such as a discotic liquid-crystal compound, to an alignment film, then heating it at a temperature higher than the alignment temperature to thereby align molecules of the liquid-crystal compound, and fixing the alignment state. In producing the optical compensatory sheet of the type, the liquid-crystal molecules therein must be controlled in a desired alignment state. One example known for controlling the alignment of liquid-crystal molecules is using an alignment layer (interface treatment). However, only by the control force of the alignment layer, it is difficult to align liquid-crystal molecules uniformly from the alignment-layer interface to the air-interface (for monodomain alignment), and some defects such as shlieren may often remain. In particular, when the ripening time in producing the sheet is shortened for improving the producibility, shlieren defects may be more remarkable. In case where the optically anisotropic layer has such shlieren defects, it is problematic in that the defects causes light scattering and therefore detracts from the optical properties of the film.
Also proposed is a method of controlling the alignment of liquid-crystal molecules by adding an additive to the optically anisotropic layer containing liquid-crystal molecules, along with (or in place of) using such an alignment layer. For example, proposed is a method of adding a compound having a fluorine-substituted alkyl group and a hydrophilic group (a sulfo group bonding to a benzene ring via a linking group), to an optically anisotropic layer, thereby controlling the tilt angle of a discotic liquid-crystal compound (for example, see JPA No. 2001-330725). Also proposed is a method of adding a hydrophobic compound having an excluded volume effect to an optically anisotropic layer, thereby controlling the alignment of a liquid-crystal compound (for example, see JPA No. 2002-20363). Also proposed is a fluoroaliphatic group-containing copolymer as an additive capable of promoting the hybrid alignment of a liquid-crystal compound and contributing toward improving the coatability thereof (for example, see JPA Nos. 2004-198511, 2005-164628).